This invention relates to a compact hydraulic pressure controller for use in e.g. a vehicle brake system, comprising a hydraulic unit and an electronic control unit joined to the hydraulic unit for controlling the hydraulic unit.
Modern motor vehicles are equipped with various hi-tech devices such as an anti-lock brake system (ABS), which obviates imminent lock-up of any vehicle wheel, thereby achieving optimum and efficient braking, a vehicle stability control (VSC) system, which controls brake pressures in individual wheel cylinders to keep a stable state of the vehicle, and a traction control (TRC) system. These devices have an electronic control unit (ECU) for controlling the entire system to adjust hydraulic pressures to the individual wheel cylinders.
The hydraulic unit, which includes solenoid valves and an actuator such as a pump unit, the motor, and the ECU are usually joined together to form a hydraulic pressure controller module because such a module is compact and low in manufacturing cost. In joining the electronic control unit to the block of the hydraulic unit, it was necessary to determine the size of the block of the hydraulic unit according to the size of the housing of the electronic control unit or vice versa.
Such a module is disclosed in unexamined JP patent publication 2000-255415 (Publication 1). This hydraulic pressure controller module has mounting protrusions provided outside of the perimeter of the housing of the electronic control unit. Joint members such as threaded bolts are passed through the mounting protrusions and the block of the hydraulic unit to join the block to the housing. The hydraulic pressure controller module disclosed in this publication further includes a motor joined to the hydraulic unit. It is an element of a vehicle brake hydraulic pressure control system.
In the arrangement of this publication, because the mounting protrusions are provided outside of the perimeter of the housing, it is necessary that the block of the hydraulic unit have a greater cross-section than the housing of the electronic control unit. This leads to increased volume (size) of the block, and thus increased cost and weight of the block.
JP patent publication 2-502900 (Publication 2) discloses a similar device, though its ECU is not joined to the block of the hydraulic unit. But this publication proposes to provide a cover that is fixed to the block of the hydraulic unit to protect portions of electric parts of solenoid valves provided on the block of the hydraulic unit that protrude from the block. The cover is formed of such a material that electric lines can be provided therein. Also, power supply means is mounted in the cover. The hydraulic unit includes only flow passages and the solenoid valves, that is, it does not include hydraulic pumps.
In one embodiment of this publication, a downwardly extending skirt is formed on the bottom end of the block of the hydraulic unit, and the skirt is fitted in the block of the hydraulic unit to mount the cover to the block. In another embodiment of this publication, claws are formed on the skirt of the block of the hydraulic unit, and the claws are engaged in grooves formed in the block to join the cover to the block body.
Unexamined JP patent publication 2002-539017 (Publication 3) also discloses a similar structure. In this publication, a substantially U-shaped claw is formed on the skirt of the cover, and the claw is engaged in a groove formed in the block, thereby elastically binding the block from outside. This ensures sealability of a seal member (O-ring) provided between the claw and the top end of the block.
As described above, Publication 1 discloses a hydraulic pressure controller module comprising a hydraulic unit and an ECU joined to the block of the hydraulic unit. As explained above, since the mounting protrusions are provided outside of the perimeter of the housing of the ECU, the size of the housing of the ECU is determined by the size of the block of the hydraulic unit, and vice versa. The block of the hydraulic unit is formed of an expensive material such as an aluminum alloy. Thus, it is desirable that such a block be as small in size (volume) as possible to reduce the material cost. On the other hand, in order to perform sophisticated control of the vehicle, it is necessary to use a circuit board that is sufficiently large in area. In order to accommodate such a large circuit board, a correspondingly large housing is needed. If such a large housing is used to accommodate a sufficiently large circuit board, it is necessary to use a correspondingly large hydraulic unit block. This pushes up the material cost. If a smaller hydraulic unit block is used, the size of the housing of the ECU has to be correspondingly reduced. Such a small housing may not be capable of accommodating a sufficiently large circuit board.
As mentioned above, Publication 2 teaches joining the cover, which is far lighter in weight than an electronic control unit, to the block of the hydraulic unit by means of the claws provided on the short skirt of the cover. It is apparent that such claws and skirt cannot reliably join a much heavier ECU to the block of a hydraulic unit. Of course, Publication 2 does not suggest using such a joint arrangement to connect an ECU to the block of a hydraulic unit. This is true for the joint arrangement disclosed in Publication 3, too.
In order for a seal member provided between the cover and the hydraulic unit to exhibit sufficient sealability, sufficiently large binding force is needed. It is apparent that such a large binding force is not obtainable only with claws formed on the resin cover as disclosed in Publication 3. Rather, due to stress concentration on the claws, creeping tends to occur. Creeping lowers sealability. Further, since such claws are provided discontinuously, no uniform binding force is obtainable. That is, at portions remote from the claws, binding force tends to be low, which lowers sealability.
An object of this invention is to provide a hydraulic pressure controller which comprises a hydraulic unit and an electronic control unit joined to the hydraulic unit and in which the dimensions of the housing of the electronic control unit and the dimensions of the block of the hydraulic unit can be determined freely independently of each other.